Hereinbefore, a macromonomer wherein polymerizable groups are introduced into the both terminal positions of polydimethyl siloxane has been used as a material of CL. However, the macromonomer is difficult to be synthesized and there have been problems in control of its molecular weight and introduction rate of the polymerizable groups, and further, there has been a restriction in obtaining suitable properties for functioning as a cross-linking agent. Still further, its polymerizability is not certain because it is high molecular weight, and thus it has been pointed out such a problem that stable polymerization is sometimes not attainable.
A polycarbonate resin has been used as an alternative material in various usages because of its transparency. There are disclosed that a polycarbonate resin obtained by reacting (1) bis (4-hydroxyphenyl)fluorene, (2) a polysiloxane, and upon necessity (3) a bisphenol with a compound forming a carbonic acid ester in Japanese Patent Publication No. 2002-284871A, a polycarbonate resin obtained by reacting the compound (1) and the compound (2) with a compound forming a carbonic acid ester in Japanese Patent Publication No. 2001-131279A and a polycarbonate resin obtained by reacting the compound (1), the compound (2) and the compound (3) with a compound forming a carbonic acid ester in Japanese Patent Publication No. 2001-342247A show, respectively, moldability, transparency and double refraction suitable to an optical material. The polycarbonates disclosed herein have advantages such as easy synthesis and purification and in molecular weight control. But, there is no specific disclosure of using the resin particularly as CL, and no study has been made on oxygen permeability and other characteristics necessary to use it as CL nor on moldability capable of giving CL or a molded article analogous to a form of CL. Further, those materials themselves are rigid and thus are not suitable to a cultivation substrate and an ophthalmic material.
On the other hand, a method of polymerizing a hydrophilic monomer under addition of a polymer, particularly polyacrylate for improving a gel strength has been known. But, there is such a problem that when polymerization is conducted under addition of a polydimethyl siloxane or polycarbonate as a polymer, there causes sticky property originated from a silicone in a case of polydimethyl siloxane and no gas permeability desired is obtained, though the strength is increased in a case of polycarbonate. Further, when its amount to be added is increased, transparency cannot be kept and thus it is not suitable as a lens material.